Cav gave a very public denial in his interveiw on eurosport after the stage and also in the post stage press conference. Also there's this piece in the daily peleton
1622 CEST - More about the Cavendish on fire (and Etna's ashes) affair. The Brit is NOT guilty according to Paolo Savoldelli: the Italian, still following the race on a RAI motorbike, carried out his own 'investigations' in the peloton, and found out that Frodo had at least three teammates around to help, that the jury cars were NOT far enough to be unable to realize any eventual cheating, and that (there comes Twitter again...) Francesco Chicchi thanked HTC for helping him to make it to the finish in time. Plus, according to the Falcon, Cav is strong enough and doesn't need such 'helping'.
http://www.dailypeloton.com/displayarticle.asp?pk=18704